import java.util.Scanner;

/**
 * Created by dllo on 18/3/30.
 */
public class NO1 {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        while (true) {

            System.out.println("请输入 数字");

            int num = scanner.nextInt();
            int sum = 0;
            for (int i = 1; i <= num; i++) {
                sum += i;
            }
            System.out.println(sum);

        }










    }
}
